Functionalities enhancement by an anisotropic strain competition

It is generally believed that epitaxial thin films are subject to compressive strain by the nearest layer with a smaller lattice constant or to tensile strain by the nearest layer with a larger lattice constant. Our experimental and theoretical results show that the above viewpoint is not always effective if the interface is anisotropic in the plane. We propose a novel strain mechanism that takes into account the pre-strain state as a key factor rather than considering only the lattice mismatch. Therefore, this anomalous strain model is potentially important for various multifunctional devices based on strain coupling.